pyopengl gluLookAt() 清晰度

Question

我试图了解我在通过 x 轴和 z 轴显示两个不同的立方体并使用网格时做错了什么。我使用 gluLookAt() 以相同的角度查看两个立方体。我很困惑为什么第一个视口不显示网格但第二个视口却显示网格。这是我的代码和示例图片，说明了我为什么感到困惑。

def draw(c1, c2):
    glClearColor(0.7, 0.7, 0.7, 0)
    glClear(GL_COLOR_BUFFER_BIT|GL_DEPTH_BUFFER_BIT)
    glBegin(GL_LINES)
    for edge in grid_edges:
        for vertex in edge:
            glColor3fv((0.0, 0.0, 0.0))
            glVertex3fv(grid_vertices[vertex])
    glEnd()

    glViewport(0, 0, WIDTH // 2, HEIGHT)
    glLoadIdentity()
    gluPerspective(90, (display[0] / display[1]) / 2, 0.1, 50.0) 
    gluLookAt(c1.center_pos[0], c1.center_pos[1], c1.center_pos[2] + 8, c1.center_pos[0], c1.center_pos[1], c1.center_pos[2], 0, 1, 0)


    glPushMatrix()
    glTranslatef(c1.center_pos[0], c1.center_pos[1], c1.center_pos[2])
    glRotatef(c1.rotation[0], c1.rotation[1], c1.rotation[2], c1.rotation[3])
    glTranslatef(-c1.center_pos[0], -c1.center_pos[1], -c1.center_pos[2])
    glBegin(GL_LINES)
    for edge in c1.edges:
        for vertex in edge:
            glColor3fv((0, 0, 0))
            glVertex3fv(c1.vertices[vertex])
    glEnd()
    glPopMatrix()

    glViewport(WIDTH // 2, 0, WIDTH // 2, HEIGHT)
    glLoadIdentity()
    gluPerspective(90, (display[0] / display[1]) / 2, 0.1, 50.0) 
    gluLookAt(c2.center_pos[0], c2.center_pos[1], c2.center_pos[2] + 8, c2.center_pos[0], c2.center_pos[1], c2.center_pos[2], 0, 1, 0)
    glPushMatrix()
    glTranslatef(c2.center_pos[0], c2.center_pos[1], c2.center_pos[2])
    glRotatef(c2.rotation[0], c2.rotation[1], c2.rotation[2], c2.rotation[3])
    glTranslatef(-c2.center_pos[0], -c2.center_pos[1], -c2.center_pos[2])
    glBegin(GL_LINES)
    for edge in c2.edges:
        for vertex in edge:
            glColor3fv((0, 0, 0))
            glVertex3fv(c2.vertices[vertex])
    glEnd()
    glPopMatrix()

Answer 1

OpenGL 是一个状态机。一旦设置了状态，它甚至会在帧之外持续存在。这意味着如果您更改视口或设置矩阵，则该视口和矩阵在下一帧开始时是相同的。这些状态不会从一帧“重置”到下一帧。您需要在draw开始时设置视口并设置单位矩阵：

def draw(c1, c2):
    glClearColor(0.7, 0.7, 0.7, 0)
    glClear(GL_COLOR_BUFFER_BIT|GL_DEPTH_BUFFER_BIT)

    glViewport(0, 0, WIDTH, HEIGHT)
    glLoadIdentity()
    glBegin(GL_LINES)
    for edge in grid_edges:
        for vertex in edge:
            glColor3fv((0.0, 0.0, 0.0))
            glVertex3fv(grid_vertices[vertex])
    glEnd()

    # [...]